Solvent-free silicon resin continuous preparation method and system

Abstract

The invention provides a continuous preparation method and system for solvent-free silicon resin, and belongs to the technical field of silicon resin processing.The preparation method comprises the steps that siloxane and silicon resin are obtained through a saturated acid solvent hydrolysis loop procedure, a washing loop procedure, a siloxane extraction procedure and a resin preparation procedure in sequence, and HCl, a solvent and waste water are recycled; the system comprises a saturated acid solvent hydrolysis loop unit, a water washing loop unit, a siloxane extraction unit and a resin preparation unit. The environment of solvent selection, hydrolysis and washing process control, solvent recovery and separation and the like is innovated, so that all-component utilization of the raw materials is realized.

Description

Technical Field

[0001] This invention relates to the field of silicone resin processing technology, and in particular to a solvent-free continuous method and system for preparing silicone resin. Background Technology

[0002] Conventional silicone resin preparation processes are generally batch reactor processes, and the products usually contain solvents. Solvent-free silicone resins are products after the solvent has been removed.

[0003] The batch reactor process has low production efficiency and automation level, and high labor intensity, but each process is highly independent, has low control requirements and low technical content, and has been widely used in the industry. The continuous loop process has high production efficiency and is easy to automate, but each process is highly interconnected, has strict control parameter requirements and high technical content, and only a few organosilicon products have adopted this process.

[0004] Traditional resin processing typically includes steps such as hydrolysis, prepolymerization, washing, dehydration, condensation, and solvent removal, with the residence time for each step being flexibly adjustable. In contrast, the continuous loop process involves very short residence times in each step, requiring extremely high precision in hydrolysis, washing, and stratification. This necessitates not only highly efficient production processes but also strict control of the degree of polymerization throughout the entire process, necessitating the merging of prepolymerization and condensation. However, this process faces challenges such as a large range of polymerization degrees and difficulties in controlling parameters during the condensation stage.

[0005] In conventional solvent-free resin preparation processes, some low-molecular-weight, high-value-added silanes or siloxanes are mixed with the recycled solvent, while others are lost in the venting exhaust gas due to non-condensation. Processes using multi-component mixed organosilicon byproducts as raw materials for resin preparation do not effectively protect active functional groups such as Si-Si and Si-H, resulting in the destruction of many low-molecular-weight, high-value-added silanes and significant resource waste. To address these issues, innovations are needed in solvent selection, hydrolysis and washing process control, solvent recovery and separation, and other environmental aspects to achieve full utilization of raw materials. Summary of the Invention

[0006] To address the above-mentioned problems, the present invention relates to a solvent-free continuous preparation method and system for silicone resin.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A continuous method for preparing solvent-free silicone resin, wherein the siloxane recovered by the preparation method is a low-boiling-point siloxane, includes the following steps: 1) Saturated acid solvent hydrolysis loop process After the solvent, monomer A and monomer B are mixed evenly, they are hydrolyzed with saturated acid in the loop, and then separated to obtain acidic hydrolysate, which is used to enter the water washing loop. The separated saturated acid is returned to the hydrolysis reaction after replenishing the water consumed in the reaction. The separated hydrogen chloride gas is returned to the direct method methylchlorosilane monomer synthesis system as 99% HCl for recycling. 2) Water washing loop process The acidic hydrolysate undergoes multi-stage washing and multi-stage phase separation to obtain corresponding aqueous and oil phases. A portion of the aqueous phase is returned to the washing process of that stage as wash water, while the remaining aqueous phase is used as wash water in the previous stage. The oil phases are then further washed in the next stage of the aqueous phase separation process. Specifically, a portion of the primary aqueous phase from the primary phase separation is returned to the primary washing process as wash water, while the remaining primary aqueous phase is successively neutralized into a dilute brine, filtered, dialyzed, and evaporated to obtain sodium chloride. The oil-rich brine produced by filtration enters the secondary water washing process, while the dialysis desalinated water and the evaporated condensate enter the tertiary water washing process together. The oil phase from the final phase separation is treated as a neutral material and enters the coarse separation tower for further separation. 3) Siloxane extraction process Neutral materials are fed to a coarse separation tower for preliminary separation. A mixture of low-boiling-point, high-value siloxanes is recovered at the top of the tower. Resin and solvents without low-boiling-point, high-value siloxanes are recovered at the bottom of the tower and then processed by the reboiler of the coarse separation tower to obtain silicone resin containing solvent, which is then fed to the solvent recovery tower. The low-boiling-point, high-value siloxane mixture is condensed and then fed into an alkaline washing tank for alkaline washing. After alkaline washing, the liquid is separated, with the aqueous phase being returned to the alkaline washing kettle as alkaline solution; the separated oil phase is sent to a refining tower for refining, with the recovered product at the top of the tower and the solvent at the bottom. The product recovered at the top of the tower is condensed and used as a siloxane product; 4) Resin preparation process Silicone resin enters a solvent recovery tower for solvent recovery, and the top of the tower contains the recovered solvent and siloxanes with lower boiling points. The silicone resin in the solvent recovery tower bottom is processed by the reboiler of the recovery tower and then transported to a stationary reactor for polycondensation reaction to obtain silicone resin products for packaging.

[0008] Furthermore, in step 1), the solvent is a single solvent or a mixture of two or more solvents, and the solvent's δ d >15, δ h 0.5~5, δ p The pH ranges from 0.5 to 7; the solvent is insoluble in water and can remain stable in environments with pH < 3 and pH > 10 for a long time; the solvent boiling point is 110 to 200℃. Monomer A and monomer B are different chlorosilanes; Alternatively, monomer A and monomer B are chlorosilane and siloxane; Alternatively, monomer A and monomer B are high-boiling organosilicon compounds, low-boiling organosilicon compounds, or supernatant from organosilicon slurry. The average functionality of the mixture of monomer A and monomer B is controlled to be 1.5~2.

[0009] Furthermore, in step 1), when a single solvent is used, the solvent is toluene, xylene, anisole, or cyclohexanol; When using mixed solvents, the solvents are mixtures of n-butanol and 180# solvent oil, mixtures of cyclohexanol and S150 industrial solvent oil, mixtures of dichloroethyl ether and 180# solvent oil, and mixtures of chlorohexane and S150 industrial solvent oil. In step 3), the alkaline solution is either NaOH solution or NaHCO3 solution; In step 4), during the polycondensation reaction, a strong alkaline catalyst or a cationic strong acid resin catalyst is used for resin polycondensation.

[0010] Furthermore, in step 1), the hydrolysis reaction is carried out at a temperature of 0~80℃, a time of 1~60min, and a pressure of 0.01~0.1Mpa; In step 2), the temperature of each stage of water washing is 0~80℃ and the time is 5~60min.

[0011] A solvent-free silicone resin continuous preparation system is provided. The above preparation method uses the solvent-free silicone resin continuous preparation system to produce solvent-free silicone resin. The preparation system includes a saturated acid solvent hydrolysis loop unit, a water washing loop unit, a siloxane extraction unit, and a resin preparation unit. The saturated acid solvent hydrolysis loop unit includes a mixing tank, a static mixer, a hydrolysis phase separator, and a hydrolysate intermediate tank. The outlet of the mixing tank is connected to the static mixer, and a soft water inlet pipe is also provided at the inlet of the static mixer. The outlet of the static mixer is connected to the inlet in the middle of the hydrolysis phase separator. The outlet at the bottom of the hydrolysis phase separator is connected to the inlet of the static mixer. A condensation and purification device is provided at the outlet at the top. The condensation and purification device has two outlets. One outlet is used to recover HCl, and the other outlet is connected to the inlet of the hydrolysate intermediate tank. The hydrolysate intermediate tank has two outlets, which are connected to the first-stage water washing tank of the water washing loop unit and the inlet in the middle of the hydrolysis phase separator, respectively. The water washing loop unit includes a multi-stage water washing tank, a multi-stage phase separator, a neutralization tank, an ultrafiltration / nanofiltration device, a reverse osmosis device, and an evaporator; the outlet of each stage water washing tank is connected to the inlet of the corresponding stage phase separator, the outlet at the top of each stage phase separator is connected to the inlet of the next stage water washing tank, and the outlet at the bottom of each stage phase separator is connected to the inlet of the corresponding stage water washing tank and the inlet of the previous stage water washing tank. The inlet of the primary water washing tank is connected to the outlet of the intermediate tank of hydrolysate in the saturated acid solvent hydrolysis loop unit; the outlet at the bottom of the primary phase separator is connected to the inlet of the primary water washing tank and the inlet of the neutralization tank, respectively. The outlet of the neutralization tank is connected to the inlet of the ultrafiltration / nanofiltration device. The ultrafiltration / nanofiltration device has two outlets. One outlet is connected to the inlet of the secondary water washing tank and is used to transport the oil-rich brine produced by ultrafiltration / nanofiltration to the secondary water washing tank. The other outlet is connected to the reverse osmosis device and produces fresh water and concentrated water through reverse osmosis membrane permeation treatment. The fresh water outlet of the reverse osmosis device is connected to the inlet of the tertiary water washing tank, the concentrated water outlet is connected to the inlet of the evaporator, and the condensate outlet of the evaporator is connected to the inlet of the tertiary water washing tank. The outlet at the top of the last-stage phase separator is connected to the inlet of the coarse separation tower in the siloxane extraction unit. The siloxane extraction unit includes a coarse separator, an alkaline washing kettle, a phase separator, and a purification tower. The inlet of the coarse separator is connected to the outlet of the last stage intermediate washing tank in the water washing loop unit. The outlet at the bottom of the coarse separator is connected to the inlet of the solvent recovery tower in the resin preparation unit. The outlet at the top of the coarse separator is connected to both the inlet of the coarse separator and the inlet of the alkaline washing kettle. The outlet at the bottom of the alkaline washing kettle is connected to both the inlet of the alkaline washing kettle and the waste alkali tank. The outlet at the top of the phase separator is connected to the inlet of the purification tower. The outlet at the bottom of the purification tower is connected to the solvent storage tank. The outlet at the top of the purification tower is connected to both the inlet of the purification tower and the siloxane storage tank. The resin preparation unit includes a solvent recovery tower, a resin intermediate tank, a fixed-bed reactor, a cooler, a phase separator, and a solvent-free resin tank. The inlet of the solvent recovery tower is connected to the outlet of the reboiler in the coarse fractionation tower of the siloxane extraction unit. The outlet at the top of the solvent recovery tower is connected to both the inlet of the solvent recovery tower and the solvent storage tank. The outlet at the bottom of the solvent recovery tower is connected to the inlet of the fixed-bed reactor. The outlet at the top of the fixed-bed reactor is connected to the inlet of the phase separator. The outlet at the top of the phase separator is connected to the inlet of the solvent storage tank. The outlet at the bottom of the phase separator is connected to the waste alkali tank. The outlet at the bottom of the fixed-bed reactor is connected to both the inlet of the fixed-bed reactor and the inlet of the cooler, and the outlet of the cooler is connected to the inlet of the solvent-free resin tank.

[0012] A continuous method for preparing solvent-free silicone resin, wherein the siloxane recovered by the preparation method is a high-boiling-point siloxane, includes the following steps: 1) Saturated acid solvent hydrolysis loop process After the solvent, monomer A and monomer B are mixed evenly, they are hydrolyzed with saturated acid in the loop, and then separated to obtain acidic hydrolysate, which is used to enter the water washing loop. The separated saturated acid is returned to the hydrolysis reaction after replenishing the water consumed in the reaction. The separated hydrogen chloride gas is returned to the direct method methylchlorosilane monomer synthesis system as 99% HCl for recycling. 2) Water washing loop process The acidic hydrolysate undergoes multi-stage washing and multi-stage phase separation to obtain corresponding aqueous and oil phases. A portion of the aqueous phase is returned to the washing process of that stage as wash water, while the remaining aqueous phase is used as wash water in the previous stage. The oil phases are then further washed in the next stage of the aqueous phase separation process. Specifically, a portion of the primary aqueous phase from the primary phase separation is returned to the primary washing process as wash water, while the remaining primary aqueous phase is successively neutralized into a dilute brine, filtered, dialyzed, and evaporated to obtain sodium chloride. The oil-rich brine produced by filtration enters the secondary water washing process, while the dialysis desalinated water and the evaporated condensate enter the tertiary water washing process together. The oil phase from the final phase separation is treated as a neutral material and enters the solvent recovery tower for solvent recovery. 3) Resin preparation process Neutral materials enter the solvent recovery tower for solvent recovery, and the top of the tower contains the recovered solvent and siloxanes with low boiling points; The silicone resin in the solvent recovery tower bottom is processed by the reboiler of the recovery tower and then transported to a stationary reactor for polycondensation reaction to obtain silicone resin products for packaging.

[0013] The high-value siloxane mixture removed by the polycondensation reaction is condensed and phase-separated, and the oil phase is transported to the alkaline washing kettle for alkaline washing. 4) Siloxane extraction process After being condensed, the high-value siloxane mixture is transported into an alkaline washing tank for alkaline washing using alkaline solution. After alkaline washing, the liquid is separated, with the aqueous phase being returned to the alkaline washing kettle as alkali solution; the separated oil phase is sent to a refining tower for refining, with the bottom of the tower containing the recovered siloxane product and the top containing the solvent.

[0014] Furthermore, in step 1), the solvent is a single solvent or a mixture of two or more solvents, and the solvent's δ d >15, δ h 0.5~5, δ p The pH ranges from 0.5 to 7; the solvent is insoluble in water and can remain stable in environments with pH < 3 and pH > 10 for a long time; the solvent boiling point is 110 to 200℃. Monomer A and monomer B are different chlorosilanes; Alternatively, monomer A and monomer B are chlorosilane and siloxane; Alternatively, monomer A and monomer B are high-boiling organosilicon compounds, low-boiling organosilicon compounds, or supernatant from organosilicon slurry. The average functionality of the mixture of monomer A and monomer B is controlled to be 1.5~2.

[0015] Furthermore, in step 1), when a single solvent is used, the solvent is toluene, xylene, anisole, or cyclohexanol; When using mixed solvents, the solvents are mixtures of n-butanol and 180# solvent oil, mixtures of cyclohexanol and S150 industrial solvent oil, mixtures of dichloroethyl ether and 180# solvent oil, and mixtures of chlorohexane and S150 industrial solvent oil. In step 3), during the polycondensation reaction, a strong alkaline catalyst or a cationic strong acid resin catalyst is used for resin polycondensation. In step 4), the alkaline solution is either NaOH solution or NaHCO3 solution.

[0016] Furthermore, in step 1), the hydrolysis reaction is carried out at a temperature of 0~80℃, a time of 1~60min, and a pressure of 0.01~0.1Mpa; In step 2), the temperature of each stage of water washing is 0~80℃ and the time is 5~60min.

[0017] A solvent-free silicone resin continuous preparation system is provided. The above preparation method uses the solvent-free silicone resin continuous preparation system to produce solvent-free silicone resin. The preparation system includes a saturated acid solvent hydrolysis loop unit, a water washing loop unit, a siloxane extraction unit, and a resin preparation unit. The saturated acid solvent hydrolysis loop unit includes a mixing tank, a static mixer, a hydrolysis phase separator, and a hydrolysate intermediate tank. The outlet of the mixing tank is connected to the static mixer, and a soft water inlet pipe is also provided at the inlet of the static mixer. The outlet of the static mixer is connected to the inlet in the middle of the hydrolysis phase separator. The outlet at the bottom of the hydrolysis phase separator is connected to the inlet of the static mixer. A condensation and purification device is provided at the outlet at the top. The condensation and purification device has two outlets. One outlet is used to recover HCl, and the other outlet is connected to the inlet of the hydrolysate intermediate tank. The hydrolysate intermediate tank has two outlets, which are connected to the first-stage water washing tank of the water washing loop unit and the inlet in the middle of the hydrolysis phase separator, respectively. The water washing loop unit includes a multi-stage water washing tank, a multi-stage phase separator, a neutralization tank, an ultrafiltration / nanofiltration device, a reverse osmosis device, and an evaporator; the outlet of each stage water washing tank is connected to the inlet of the corresponding stage phase separator, the outlet at the top of each stage phase separator is connected to the inlet of the next stage water washing tank, and the outlet at the bottom of each stage phase separator is connected to the inlet of the corresponding stage water washing tank and the inlet of the previous stage water washing tank. The inlet of the primary water washing tank is connected to the outlet of the intermediate tank of hydrolysate in the saturated acid solvent hydrolysis loop unit; the outlet at the bottom of the primary phase separator is connected to the inlet of the primary water washing tank and the inlet of the neutralization tank, respectively. The outlet of the neutralization tank is connected to the inlet of the ultrafiltration / nanofiltration device. The ultrafiltration / nanofiltration device has two outlets. One outlet is connected to the inlet of the secondary water washing tank and is used to transport the oil-rich brine produced by ultrafiltration / nanofiltration to the secondary water washing tank. The other outlet is connected to the reverse osmosis device and produces fresh water and concentrated water through reverse osmosis membrane permeation treatment. The fresh water outlet of the reverse osmosis device is connected to the inlet of the tertiary water washing tank, the concentrated water outlet is connected to the inlet of the evaporator, and the condensate outlet of the evaporator is connected to the inlet of the tertiary water washing tank. The outlet at the top of the final phase separator is connected to the inlet of the solvent recovery tower of the resin preparation unit; The resin preparation unit includes a solvent recovery tower, a resin intermediate tank, a fixed-bed reactor, a cooler, a phase separator, and a solvent-free resin tank. The inlet of the solvent recovery tower is connected to the outlet at the top of the last-stage phase separator. The outlet at the top of the solvent recovery tower is connected to both the inlet of the solvent recovery tower and the solvent storage tank. The outlet at the bottom of the solvent recovery tower is connected to the inlet of the fixed-bed reactor. The outlet at the top of the fixed-bed reactor is connected to the inlet of the phase separator. The outlet at the top of the phase separator is connected to the inlet of the alkaline washing vessel in the siloxane extraction unit. The outlet at the bottom of the phase separator is connected to the waste alkali tank. The outlet at the bottom of the fixed-bed reactor is connected to the inlet of the fixed-bed reactor and the inlet of the cooler, respectively; the outlet of the cooler is connected to the inlet of the solvent-free resin tank. The siloxane extraction unit includes an alkaline washing kettle, a phase separator, and a purification tower. The inlet of the alkaline washing kettle is connected to the outlet at the top of the phase separator in the resin preparation unit, and the outlet of the alkaline washing kettle is connected to the inlet of the phase separator. The outlet at the bottom of the phase separator is connected to the inlet of the alkaline washing kettle and the waste alkali tank. The outlet at the top of the phase separator is connected to the inlet of the purification tower. The outlet at the bottom of the purification tower is connected to the reboiler of the purification tower. The outlet of the reboiler of the purification tower is connected to the siloxane storage tank. The outlet at the top of the purification tower is connected to a condenser. The outlet of the condenser is connected to a solvent recovery tank. The outlet of the solvent recovery tank is connected to the inlet of the purification tower and the solvent storage tank, respectively.

[0018] The beneficial effects of the solvent-free continuous preparation method and system for silicone resin of the present invention are as follows: The saturated acid solvent hydrolysis loop process of this invention can recover HCl and protect active groups. This process adopts a concentrated acid loop hydrolysis process with micro-positive pressure (gauge pressure 0.01~0.1Mpa). Its high acid value can significantly shorten the reaction time and avoid loss of active groups. The subsequent water washing process without alkali can retain active groups to the maximum extent. The micro-positive pressure saturated acid solvent hydrolysis creates a high concentration of chloride ions, which can inhibit the excessive hydrolysis of -SiCl3 and SiCl2 structures and avoid the polymer rise caused by large-scale prepolymerization. Micro-positive pressure hydrolysis can flash evaporate some high-value-added silanes under reduced pressure in the hydrolysis phase separator and efficiently precipitate HCl gas, which can significantly shorten the phase separation residence time and further avoid polymer rise and loss of active groups. After most of the water droplets are removed by the built-in demisting net at the top of the hydrolysis phase separator, the water is further condensed in the condensation purification device to obtain 99% pure HCl, which can be directly recycled to the monomer synthesis system, avoiding resource waste and significantly reducing the generation of waste acid. This invention achieves efficient and comprehensive recovery of high-value-added silanes through solvent selection and system integration. By selecting suitable solvents, the product is completely separated from the aqueous phase throughout the process, minimizing the loss of active groups. Furthermore, since the solvent boiling point is more than 20°C higher than the high-value-added silane, entrainment losses are minimal. Based on the material characteristics, this invention adds an optional alkaline washing inactivation process. For example, hexamethyldisilane has high value but a small market capacity, and most of it needs alkaline washing inactivation to convert it into another high-value-added product—hexamethyldisiloxane. This invention employs a deep-cooling process for tail gas to centrally recover high-value-added silanes volatilized from flash evaporation and various equipment, eliminating venting losses and avoiding tail gas pollution. Both solvent recovery and material separation utilize low-plate-count distillation columns, resulting in minimal energy consumption increases and avoiding material entrainment losses. The solvent boiling point range of this invention coincides with the boiling point of the higher-boiling-point component in low-molecular-weight siloxanes. This portion of the siloxane has high hydrolysis reactivity and can continue to participate in the reaction without further separation, thus preventing material loss. The overall solvent recovery rate is over 98%. This invention establishes a controllable resin polycondensation process. The product obtained after hydrolysis, washing, and solvent removal has a viscosity significantly lower than that of conventional resin processes, less than 50 cs, and can be directly used to prepare solvent-free environmentally friendly spray coatings. Considering that most coatings require high-viscosity resins, this technology also includes an optional resin polycondensation process. Based on the excellent control of product quality at the front end of this process, the chloride ion content can be controlled below 800 ppm, and the acid value is extremely low, allowing the polycondensation catalyst to be replaced with a KOH or NaOH catalyst that can be quickly and quantitatively terminated. The resin polycondensation process uses KOH or NaOH as a catalyst and carries out polycondensation at a relatively low temperature (80~110℃). By adjusting the vacuum degree and reaction time, and using phosphoric acid for quantitative and rapid termination, the product viscosity can be precisely controlled within the range of 50~10000 cs (±10%). Furthermore, the residual phosphate has an acid-base buffering effect, avoiding the impact of trace acid values ​​on storage stability of conventional silicone resins, and the shelf life exceeds 12 months. Compared to traditional processes, this invention converts acidic wastewater into 99% HCl and concentrated acid, which are used for monomer synthesis and metal processing rust removal, respectively. Only the optional alkaline washing process generates a very small amount of wastewater. Silanes in the exhaust gas are cryogenically recovered, and only inert and harmless gases such as nitrogen are released. Low-boiling-point siloxanes are converted into high-value silanes or continue to participate in hydrolysis to form silicone resins, without generating any solid waste. The resin product prepared by this invention has low chloride ion content and is stable during storage. Before the resin is prepared, the degree of polymerization is controlled at a low level throughout the process, which greatly reduces acid entrainment. The chloride ion content can be controlled below 800 ppm, which can be used to prepare various high-quality anti-corrosion coatings. The introduction of trace amounts of phosphate during the polycondensation reaction process forms an acid-base buffer system, which can extend the product's shelf life to more than 12 months. Attached Figure Description

[0019] Figure 1 This invention provides a simplified process flow diagram of the saturated acid solvent hydrolysis loop and a schematic diagram of the saturated acid solvent hydrolysis loop unit structure. Figure 2 This is a simplified process flow diagram of the water washing loop and a schematic diagram of the water washing loop unit structure of the present invention; Figure 3 This invention provides a simplified flow chart of the siloxane extraction process and a schematic diagram of the siloxane extraction unit when the siloxane is a low-boiling-point siloxane. Figure 4 This invention provides a simplified flow chart of the resin preparation process and a schematic diagram of the resin preparation unit structure when the siloxane is a low-boiling-point siloxane. Figure 5 This invention provides a simplified flow chart of the siloxane extraction process and a schematic diagram of the siloxane extraction unit when the siloxane is a high-boiling-point siloxane. Figure 6 This invention provides a simplified flow chart of the resin preparation process and a schematic diagram of the resin preparation unit structure when the siloxane is a high-boiling-point siloxane. Detailed Implementation

[0020] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Those skilled in the art can make similar extensions without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0021] This invention discloses a continuous method for preparing solvent-free silicone resin. When the siloxane is a low-boiling-point siloxane, the method uses chlorosilane and siloxane as raw materials to co-produce solvent-free silicone resin and high-value-added silane via a loop continuous process. The specific steps include: 1) Saturated acid solvent hydrolysis loop process Saturated acid solvent hydrolysis loop process such as Figure 1 As shown, solvent, monomer A, and monomer B are mixed evenly in a mixing tank, and then hydrolyzed with saturated acid solution in a loop in a static mixer. The hydrolysis reaction temperature is 0~80℃, the time is 1~60min, and the pressure is 0.01~0.1Mpa. An appropriate amount of wash water (i.e., industrial soft water and saturated acid solution separated by the hydrolysis phase separator; industrial soft water is injected before the hydrolysis circulation pump to balance the system's water consumption, and the replenishment rate is dynamically adjusted according to the phase separator interface) is added. The mixture then enters the hydrolysis phase separator for separation, and the resulting acidic hydrolysate (oil phase) enters the hydrolysate intermediate tank for entering the water washing loop. The separated saturated acid solution (aqueous phase) is discharged from the bottom of the hydrolysis phase separator and returned to the static mixer. The separated hydrogen chloride gas (gas phase) is discharged from the top of the hydrolysis phase separator. After being treated by a condensation and purification device, the liquid phase is recovered to the hydrolysate intermediate tank, and the gas phase, which is 99% HCl, is returned to the direct method methylchlorosilane monomer synthesis system for recycling. The loop water replenishment discharges excess saturated acid solution into the concentrated acid tank according to the interface of the hydrolysis phase separator.

[0022] The solvent used in this invention is a single solvent or a mixture of two or more solvents. Based on the solubility characteristics of chlorosilanes and siloxanes, the solvent δ is required. d >15, δ h 0.5~5, δ pThe concentration should be 0.5-7; and according to the hydrolysis, washing process, and recovery requirements, the solvent must be insoluble in water and able to exist stably in environments with pH < 3 and pH > 10 for a long time. Simultaneously, the solvent must be able to separate well from high-value-added silanes (boiling point generally below 110℃) and the silicone resin matrix (boiling point above 200℃), therefore, the solvent boiling point requirement is 110-200℃. Based on the above conditions, when using a single solvent, toluene, xylene, anisole, cyclohexanol, etc. are suitable. Considering the difficulty of high-purity recovery of high-value-added silanes, solvents with boiling points between 130-200℃ are recommended, such as xylene, anisole, and cyclohexanol. When using a mixed solvent, mixtures of n-butanol and 180# solvent oil, or mixtures of cyclohexanol and S150 industrial solvent oil are suitable. Considering solvent dissolution losses in the water system, mixed solvents with the lowest possible solubility are preferred. Considering environmental factors, mixtures of dichloroethyl ether and 180# solvent oil, or mixtures of chlorohexane and S150 industrial solvent oil are preferred.

[0023] The process of this invention has strong compatibility with raw materials. The monomers A and B can be of the same type, such as different chlorosilanes, or combinations of different types of substances, such as chlorosilanes and methoxysilanes. Monomers A and B can be monomers with clearly defined components, such as chlorosilanes and siloxanes, for example, dimethyldichlorosilane and monomethyltrichlorosilane; or mixtures with indeterminate components, such as high-boiling organosilicon compounds, low-boiling organosilicon compounds, and organosilicon slurry supernatant. Monomers A and B can be organochlorosilanes such as methylchlorosilane, vinylchlorosilane, and phenylchlorosilane, or methoxysilanes and acyloxysilanes with high hydrolytic reactivity. However, monomers with weak hydrolytic reactivity, such as ethoxysilanes and methyl-terminated siloxanes, cannot be selected.

[0024] The average functionality of the mixture of monomers A and B is controlled at 1.5~2. If the content of indeterminate mixtures in the raw materials exceeds 10%, the average functionality of the mixture must be determined according to the spectrum and the deviation must be controlled within ±0.1. Considering the stability of industrial operation, the control range of average functionality is narrowed to 1.8~2.

[0025] When monomers A and B are chlorosilanes, the general formula for the hydrolysis reaction is as follows: SiCl a R （4-a） +a / 2H₂O=SiO a / 2R （4-a） +aHCl (unlimited); Si2ClbR （8-b） +b / 2H₂O=Si₂Ob / 2R （8-b） +bHCl (neutral or acidic); Si2Cl c R （8-c） +(c / 2+1)H2O=Si2O（c / 2+1） R （8-c） +cHCl + H2↑ (Alkaline, the reaction is complete in a strong alkaline environment, and partially in a weak alkaline environment). SiH d R （4-d） +d / 2H₂O=SiO （d / 2） R （4-d） +dH2↑ (Alkaline, complete reaction in strong alkaline environments, partial reaction in weak alkaline environments; trace reaction in strong acidic systems).

[0026] When monomers A and B are alkoxysilanes, the general formula for the hydrolysis reaction is as follows: Si (OR) a R' （4-a） +a / 2H₂O=SiO a / 2 R' （4-a） +aROH (acidic, basic; no reaction in neutral) The side reactions in the hydrolysis loop of saturated acid solvent are as follows: ROH + HCl = RCl + H2O (affects ROH recovery).

[0027] 2) Water washing loop process Water washing loop process such as Figure 2 As shown, the acidic hydrolysate in the intermediate hydrolysate tank enters the primary water washing tank for primary water washing, and then is separated by the primary phase separator. The separated primary aqueous phase is returned to the primary water washing tank to wash the acidic hydrolysate. The remaining primary aqueous phase (i.e., acidic wash water) is neutralized into dilute brine by soda ash in the neutralization tank (part of the alkali solution comes from the waste alkali tank), filtered by ultrafiltration / nanofiltration, dialyzed by reverse osmosis membrane, and evaporated by evaporator to obtain sodium chloride. Among them, the oil-rich brine produced by ultrafiltration / nanofiltration enters the secondary water washing tank for secondary water washing, and the dilute water from reverse osmosis membrane dialysis and the condensate from evaporation enter the tertiary water washing tank for tertiary water washing. The separated primary oil phase enters the secondary water washing tank for secondary water washing, and then is separated by the secondary phase separator. The separated secondary aqueous phase is partially returned to the secondary water washing tank for secondary water washing, and the remainder is returned to the primary water washing tank for primary water washing. The separated secondary oil phase enters the tertiary water washing tank, and is washed with raw water for tertiary water washing. Then it is separated by the tertiary phase separator. The separated tertiary oil phase (i.e., the neutral material after water washing) is stored in the tertiary water washing intermediate tank and used for further separation in the coarse separation tower (when the siloxane is a low-boiling-point siloxane, i.e., the boiling point of the siloxane is 80~120℃). The separated tertiary aqueous phase is partially returned to the tertiary water washing tank for tertiary water washing, and the remainder is sent to the secondary water washing tank for secondary water washing.

[0028] The temperature in the primary, secondary, and tertiary washing tanks is 0-80℃, and the residence time is 5-60 minutes. Each washing tank is equipped with a 20-50kHz ultrasonic breakup device to break up small oil droplets during the washing process, allowing water to fully contact with chlorosilane, avoiding SiCl residue and acid entrainment in the oil droplets, and significantly improving the washing effect. A star-shaped flocculant is installed at the inlet of the phase separator to accelerate the coagulation of the ultrasonically broken oil droplets, ensuring the phase separation effect.

[0029] The water washing loop of the present invention does not require the alkaline washing step in the traditional process. The alkaline washing step of the present invention is set in the siloxane extraction process and is not simply used for acid removal.

[0030] This invention employs a classic tiered water replenishment process, replenishing soft water only in the third-stage washing tank, while the remaining stages are replenished by the water from the next stage. This results in low water consumption, and the wastewater is entirely concentrated acid, which can be reused as a rust remover in the metal processing industry.

[0031] 3) Siloxane extraction process Siloxane extraction process as follows Figure 3 As shown, when the neutral material after washing is transported from the three-stage washing intermediate tank to the coarse separation tower for preliminary separation, a low-boiling-point, high-value siloxane mixture containing a small amount of solvent is recovered at the top of the tower. The resin and solvent without high-value silanes are recovered at the bottom of the tower. The product recovered from the bottom of the tower is processed by the reboiler of the coarse separation tower to obtain silicone resin containing solvent, which is then pumped to the solvent recovery tower. Since most of the low-boiling-point siloxane mixtures are high-value-added substances, and active groups such as Si-H (silicon-hydrogen bonds) and Si-Si (silicon-silicon bonds) are highly stable in acidic systems but severely damaged in alkaline systems, the preceding processes in this procedure are all acidic hydrolysis and washing, with no alkaline washing process. Most of the active groups in the low-boiling-point siloxane mixture can be stably preserved until the siloxane extraction process.

[0032] The low-boiling-point siloxane mixture is condensed in a condenser and then temporarily stored in the condensate tank of the coarse separator. It then enters the alkaline washing tank, where it is combined with the silane recovered from the tail gas condenser via the tail gas main. Alkaline washing is then performed in the alkaline washing tank using alkaline solution. If the low-boiling-point siloxane mixture in the coarse separator condensate tank contains a high amount of solvent, it can be reintroduced into the coarse separator for further separation.

[0033] The alkali solution is either NaOH or NaHCO3 solution supplied from the alkali solution preparation tank. If the product in the alkali washing kettle needs to retain active groups, soft water can be added to the alkali washing kettle to remove the active groups and recover any small amount of acid entrained in the siloxane from the tail gas main. After the tail gas condenser recovers the silane, the remaining gas goes to the venting system.

[0034] After alkaline washing, the liquid is separated by a phase separator. The aqueous phase is partially refluxed back to the alkaline washing kettle as alkali solution via a reflux pump, while the remaining aqueous phase (i.e., alkaline washing waste liquid) is temporarily stored in a waste alkali solution tank. The separated oil phase is pumped to a refining tower for purification to remove solvent entrained in high-value silanes. The top of the tower contains the recovered product (purity above 99%), while the bottom contains the solvent. The solvent in the bottom is further recovered by the reboiler in the refining tower and then pumped to a solvent storage tank. The product recovered from the top of the tower is condensed by a condenser and stored in a siloxane recovery tank, then pumped back to a siloxane storage tank for subsequent packaging as a siloxane product. If there is a large amount of low-boiling-point siloxane components that need to be separated, they are returned to the refining tower for re-purification. The refining tower separates the solvent from the low-boiling-point siloxanes. The solvent is recovered to the solvent storage tank, and the low-boiling-point siloxanes are packaged and sold.

[0035] 4) Resin preparation process Resin preparation process as follows Figure 4 As shown, the silicone resin containing solvent obtained from the coarse fractionation tower reboiler is fed into the solvent recovery tower for solvent recovery. The top of the tower contains the recovered solvent and low-boiling-point siloxanes, which are condensed by a condenser and then transported to the solvent recovery tank. Part of the recovered solvent is pumped to the solvent storage tank via a reflux pump, and the remainder is returned to the solvent recovery tower for further recovery. Using a solvent recovery tower to recover solvent reduces solvent entrainment in the resin compared to batch distillation.

[0036] The silicone resin in the solvent recovery tower bottom is processed by the reboiler of the recovery tower and then temporarily stored in the intermediate resin tank. It is then transferred to a stationary reactor for polycondensation reaction. During the polycondensation reaction, the material in the stationary reactor is circulated according to the requirements for the degree of polymerization of silicone resin, product viscosity range of 50~1000cs, and solid content ≥99%. After the reaction reaches the qualified index, it is condensed by the condenser and then transferred to the solvent-free resin tank for temporary storage. The silicone resin temporarily stored in the solvent-free resin tank is packaged as the final silicone resin product.

[0037] A small amount of low-boiling-point siloxane formed during the polycondensation reaction is condensed in a condenser, then dehydrated in a phase separator, and recovered to a solvent storage tank to be used as a solvent in the hydrolysis reaction. The resin polycondensation condensate waste liquid generated during the phase separator dehydration process is transported to a waste alkali tank and used together with the alkali washing waste liquid generated in the siloxane extraction process in the neutralization tank of the water washing loop to neutralize the acidic wash water, achieving zero wastewater discharge.

[0038] In the polycondensation reaction, strong alkaline catalysts such as KOH and NaOH, or cationic strong acid resin catalysts, are used for resin polycondensation. For resin products requiring the removal of SiH and Si-Si groups, a strong alkaline catalyst is selected, with phosphoric acid used as a terminator. For resin products requiring the retention of SiH and Si-Si groups, a cationic strong acid resin catalyst is used. Compared to traditional organometallic catalysts such as organozinc and organotin catalysts, the catalysts used in this invention leave no reactive residue, eliminating the need for secondary washing and extending the resin's shelf life. Because strong acid and strong base catalysts are more active than organometallic catalysts, enhanced mass and heat transfer and the use of lower ratios to control activity are necessary. In terms of mass and heat transfer, this invention employs an internally baffled fixed-bed reactor, which narrows the material channel to facilitate mass and heat transfer. The outlet is a falling film evaporator structure, which facilitates the evaporation and removal of small molecules. In terms of activity control, the chloride ion control in the pre-stage reaches 300 ppm, providing a basis for the application of low-proportion catalysts (avoiding catalyst poisoning). The addition ratio of strong alkaline catalysts is controlled at 50~500 ppm (the lower limit is chloride ion content + 50 ppm), and the addition ratio of strong acidic catalysts is controlled at 100~300 ppm (based on the mass of H2SO4 converted from the loaded acid, unaffected by chloride ion content).

[0039] This invention utilizes the acid-base stability, water insolubility, and significant boiling point difference between medium- and high-boiling-point solvents and the product to formulate a process that allows for the co-recovery of low-boiling-point components with the solvent without separation, achieving a comprehensive solvent recovery rate of over 98%. By leveraging the different sensitivities of active groups to acidic and alkaline environments, low-boiling-point siloxanes containing active groups are selectively recovered. Combined with a cryogenic tail gas recovery process, this further enhances resource utilization and industrial profitability. The silicone resin exhibits high activity, low chloride ion content, and low viscosity, making it suitable for preparing solvent-free coatings, aligning with the development direction of green coatings. The main product of this process is concentrated hydrochloric acid, with most of the HCl being recycled for monomer synthesis, resulting in minimal pollution.

[0040] This invention is a continuous preparation system for solvent-free silicone resin. The above-mentioned preparation method uses this preparation system to produce solvent-free silicone resin. When the siloxane is a low-boiling-point siloxane, the preparation system includes a saturated acid solvent hydrolysis loop unit, a water washing loop unit, a siloxane extraction unit, and a resin preparation unit. Among them, the saturated acid solvent hydrolysis loop unit is as follows: Figure 1As shown, the system includes a solvent storage tank, a monomer A storage tank, a monomer B storage tank, a mixing vessel, a static mixer, a hydrolysis phase separator, and a hydrolysate intermediate tank. The mixing vessel inlet is connected to the solvent storage tank, the monomer A storage tank, and the monomer B storage tank, respectively, and the outlet is connected to the static mixer. The static mixer inlet is also equipped with a soft water inlet pipe. The static mixer outlet is connected to the inlet in the middle of the hydrolysis phase separator. The outlet at the bottom of the hydrolysis phase separator is connected to the inlet of the static mixer. A condensation and purification device is installed at the top outlet. The condensation and purification device has two outlets: one outlet is used to recover HCl with a purity of 99%, and the other outlet is connected to the inlet of the hydrolysate intermediate tank. The hydrolysate intermediate tank has two outlets, one connected to the first-stage water washing vessel of the water washing loop unit, and the other connected to the inlet in the middle of the hydrolysis phase separator.

[0041] Water washing loop unit such as Figure 2 As shown, the system includes a primary water washing tank, a primary phase separator, a primary water washing intermediate tank, a secondary water washing tank, a secondary phase separator, a secondary water washing intermediate tank, a tertiary water washing tank, a tertiary phase separator, a tertiary water washing intermediate tank, a neutralization tank, an ultrafiltration / nanofiltration device, a reverse osmosis device, and an evaporator. The inlet of the primary water washing tank is connected to the outlet of the intermediate tank of the saturated acid solvent hydrolysis loop unit, the bottom outlet of the primary phase separator, and the bottom outlet of the secondary phase separator. The outlet of the primary water washing tank is connected to the inlet in the middle of the primary phase separator. The outlet at the top of the primary phase separator is connected to the inlet of the primary water washing intermediate tank. The bottom outlet is connected to the inlet of the primary water washing tank and the inlet of the neutralization tank. The outlet of the neutralization tank is connected to the inlet of the ultrafiltration / nanofiltration device. The ultrafiltration / nanofiltration device has two outlets: one outlet is connected to the inlet of the secondary water washing tank to transport the oil-rich brine produced by ultrafiltration / nanofiltration to the secondary water washing tank, and the other outlet is connected to the reverse osmosis device. The system is interconnected, producing fresh and concentrated water through reverse osmosis membrane treatment. The fresh water outlet of the reverse osmosis unit is connected to the inlet of the tertiary water washing tank, the concentrated water outlet is connected to the inlet of the evaporator, and the condensate outlet of the evaporator is connected to the inlet of the tertiary water washing tank. The outlet of the primary water washing intermediate tank is connected to the inlet of the secondary water washing tank, the outlet of the secondary water washing tank is connected to the inlet of the middle part of the secondary phase separator, the bottom outlet of the secondary phase separator is connected to both the inlet of the secondary water washing tank and the inlet of the primary water washing tank, the upper outlet of the secondary phase separator is connected to the inlet of the secondary water washing intermediate tank, the outlet of the secondary water washing intermediate tank is connected to the inlet of the tertiary water washing tank, the outlet of the tertiary water washing tank is connected to the inlet of the middle part of the tertiary phase separator, the bottom outlet of the tertiary phase separator is connected to both the inlet of the tertiary water washing tank and the inlet of the secondary water washing tank, the upper outlet of the tertiary phase separator is connected to the tertiary water washing intermediate tank, and the outlet of the tertiary water washing intermediate tank is connected to the inlet of the coarse separation tower in the siloxane extraction unit.

[0042] Siloxane extraction unit such as Figure 3As shown, the system includes a coarse separator, an alkaline washing kettle, a phase separator, and a refining tower. The inlet of the coarse separator is connected to the outlet of the intermediate tank in the three-stage water washing loop unit. A reboiler is connected to the bottom outlet of the coarse separator, and the outlet of the reboiler is connected to the inlet of the solvent recovery tower in the resin preparation unit. A condenser is connected to the top outlet of the coarse separator, and a condensate tank is connected to the outlet of the condenser. The condensate tank is connected to both the inlet of the coarse separator and the inlet of the alkaline washing kettle via a reflux pump. An alkali preparation tank is also connected to the inlet of the alkaline washing kettle. It is also connected to the tail gas condenser, and the outlet of the alkali washing kettle is connected to the inlet of the middle part of the phase separator; the outlet at the bottom of the phase separator is connected to the inlet of the alkali washing kettle and the waste alkali tank via a reflux pump, the outlet at the top of the phase separator is connected to the inlet of the purification tower via a transfer pump, the outlet at the bottom of the purification tower is connected to the reboiler of the purification tower, the outlet of the reboiler of the purification tower is connected to the solvent storage tank via a transfer pump, the outlet at the top of the purification tower is connected to the condenser, the outlet of the condenser is connected to the siloxane recovery tank, and the outlet of the siloxane recovery tank is connected to the inlet of the purification tower and the siloxane storage tank via a reflux pump.

[0043] Resin preparation unit such as Figure 4 As shown, the system includes a solvent recovery tower, a resin intermediate tank, a fixed-bed reactor, a cooler, a phase separator, and a solvent-free resin tank. The inlet of the solvent recovery tower is connected to the outlet of the reboiler in the coarse fractionation tower of the siloxane extraction unit. A condenser is connected to the outlet at the top of the solvent recovery tower, and a solvent recovery tank is located at the outlet of the condenser. The outlet of the solvent recovery tank is connected to both the inlet of the solvent recovery tower and the solvent storage tank via a reflux pump. A reboiler is located at the outlet at the bottom of the solvent recovery tower, and its outlet is connected to the inlet of the resin intermediate tank via a transfer pump. The outlet of the resin intermediate tank is connected to the inlet of the fixed-bed reactor. A condenser is located at the outlet at the top of the fixed-bed reactor, and its outlet is connected to the inlet of the phase separator. The upper outlet of the phase separator is connected to the inlet of the solvent storage tank, and the bottom outlet of the phase separator is connected to the waste alkali tank. The bottom outlet of the fixed-bed reactor is connected to both the inlet of the fixed-bed reactor and the inlet of the cooler. The outlet of the cooler is connected to the inlet of the solvent-free resin tank.

[0044] This invention discloses a solvent-free continuous method for preparing silicone resin. When the siloxane is a high-boiling-point siloxane, the preparation method includes the following steps: 1) Saturated acid solvent hydrolysis loop process Saturated acid solvent hydrolysis loop process such as Figure 1 As shown, the process is exactly the same as described above.

[0045] 2) Water washing loop process Water washing loop process such as Figure 2As shown, the process is basically the same as the above process, except that the third-stage oil phase (i.e., the neutral material after water washing) separated by the three-stage phase separator is stored in the third-stage water washing intermediate tank and is used to enter the solvent recovery tower for recovery (when the siloxane is a high-boiling-point siloxane, i.e., the boiling point of the siloxane is 180~250℃).

[0046] 3) Resin preparation process Resin preparation process as follows Figure 5 As shown, when the neutral material after washing is transported from the three-stage washing intermediate tank to the solvent recovery tower for solvent recovery, the top of the tower contains the recovered solvent and low-boiling-point siloxanes. After condensation by the condenser, these are transported to the solvent recovery tank. Part of the recovered solvent is transported to the solvent storage tank via a reflux pump, and the remainder is returned to the solvent recovery tower for further recovery. Using a solvent recovery tower to recover solvent reduces solvent entrainment in the resin compared to batch distillation.

[0047] The silicone resin in the solvent recovery tower bottom is processed by the reboiler of the recovery tower and then temporarily stored in the intermediate resin tank. It is then transferred to a fixed reactor for polycondensation reaction. During the polycondensation reaction, the material in the fixed reactor is circulated according to the requirements for the degree of polymerization of silicone resin, product viscosity range of 50~1000cs, and solid content ≥99%. After the reaction reaches the qualified index, it is condensed by a cooler and then transferred to a solvent-free resin tank for temporary storage. The silicone resin temporarily stored in the solvent-free resin tank is packaged as the final silicone resin product.

[0048] The high-value siloxane mixture formed during the polycondensation reaction is condensed in a condenser and then dehydrated in a phase separator. The recovered oil phase is then transported to an alkaline washing tank for further treatment. The resin polycondensation condensate waste liquid generated during the phase separator dehydration process is transported to a waste alkali tank and, together with the alkaline washing waste liquid generated in the siloxane extraction process, is used in the neutralization tank of the water washing loop process to neutralize the acidic wash water, achieving zero wastewater discharge.

[0049] In the polycondensation reaction, strong alkaline catalysts such as KOH and NaOH, or cationic strong acid resin catalysts, are used for resin polycondensation. For resin products requiring the removal of SiH and Si-Si groups, a strong alkaline catalyst is selected, with phosphoric acid used as a terminator. For resin products requiring the retention of SiH and Si-Si groups, a cationic strong acid resin catalyst is used. Compared to traditional organometallic catalysts such as organozinc and organotin catalysts, the catalysts used in this invention leave no reactive residue, eliminating the need for secondary washing and extending the resin's shelf life. Because strong acid and strong base catalysts are more active than organometallic catalysts, enhanced mass and heat transfer and the use of lower ratios to control activity are necessary. In terms of mass and heat transfer, this invention employs an internally baffled fixed-bed reactor, which narrows the material channel to facilitate mass and heat transfer. The outlet is a falling film evaporator structure, which facilitates the evaporation and removal of small molecules. In terms of activity control, the chloride ion control in the pre-stage reaches 300 ppm, providing a basis for the application of low-proportion catalysts (avoiding catalyst poisoning). The addition ratio of strong alkaline catalysts is controlled at 50~500 ppm (the lower limit is chloride ion content + 50 ppm), and the addition ratio of strong acidic catalysts is controlled at 100~300 ppm (based on the mass of H2SO4 converted from the loaded acid, unaffected by chloride ion content).

[0050] 4) Siloxane extraction process Siloxane extraction process as follows Figure 6 As shown, the high-value siloxane mixture removed during the polycondensation reaction is condensed in a condenser and dehydrated in a phase separator. The recovered oil phase is then transported to an alkaline washing reactor, where it is combined with the silane recovered from the tail gas condenser that enters from the tail gas main pipe. Alkaline washing is then performed in the alkaline washing reactor using alkaline solution.

[0051] The alkali solution is either NaOH or NaHCO3 solution supplied from the alkali solution preparation tank. If the product in the alkali washing kettle needs to retain active groups, soft water can be added to the alkali washing kettle to remove the active groups and recover any small amount of acid entrained in the siloxane from the tail gas main. After the tail gas condenser recovers the silane, the remaining gas goes to the venting system.

[0052] After alkaline washing, the liquid is separated by a phase separator. The aqueous phase is partially refluxed back to the alkaline washing kettle as alkali solution via a reflux pump, while the remaining aqueous phase (i.e., alkaline washing waste liquid) is temporarily stored in a waste alkali solution tank. The separated oil phase is pumped to a refining tower for purification to remove solvent entrained in high-value silanes. The top of the tower contains the solvent, and the bottom contains the recovered product (purity above 99%). The bottom product is further recovered by the reboiler in the refining tower and then pumped to the siloxane storage tank. The solvent recovered from the top of the tower is condensed by a condenser and stored in a solvent recovery tank, then pumped back to the solvent storage tank via a reflux pump. If there is a large amount of low-boiling-point solvent components that need to be separated, they are returned to the refining tower for re-purification. The refining tower separates the solvent from the high-boiling-point siloxanes. The solvent is recovered to the solvent storage tank, and the high-boiling-point siloxanes are packaged and sold.

[0053] This invention is a continuous preparation system for solvent-free silicone resin. The above-mentioned preparation method uses this preparation system to produce solvent-free silicone resin. When the siloxane is a high-boiling-point siloxane, the preparation system includes a saturated acid solvent hydrolysis loop unit, a water washing loop unit, a siloxane extraction unit, and a resin preparation unit. Among them, the saturated acid solvent hydrolysis loop unit is as follows: Figure 1 As shown, it includes a solvent storage tank, a monomer A storage tank, a monomer B storage tank, a mixing vessel, a static mixer, a hydrolysis phase separator, and a hydrolysate intermediate tank, and their connection relationship is exactly the same as that of the above-mentioned saturated acid solvent hydrolysis loop unit.

[0054] Water washing loop unit such as Figure 2 As shown, it includes a primary water washing tank, a primary phase separator, a primary water washing intermediate tank, a secondary water washing tank, a secondary phase separator, a secondary water washing intermediate tank, a tertiary water washing tank, a tertiary phase separator, a tertiary water washing intermediate tank, a neutralization tank, an ultrafiltration / nanofiltration device, a reverse osmosis device, and an evaporator; its connection relationship is almost the same as the above-mentioned water washing loop unit, the only difference being that the outlet of the tertiary water washing intermediate tank is connected to the inlet of the solvent recovery tower of the resin preparation unit.

[0055] Resin preparation unit such as Figure 5 As shown, the system includes a solvent recovery tower, a resin intermediate tank, a fixed-bed reactor, a cooler, a phase separator, and a solvent-free resin tank. The inlet of the solvent recovery tower is connected to the outlet of the three-stage water washing intermediate tank in the water washing loop unit. A condenser is connected to the outlet at the top of the solvent recovery tower, and a solvent recovery tank is located at the outlet of the condenser. The outlet of the solvent recovery tank is connected to both the inlet of the solvent recovery tower and the solvent storage tank via a reflux pump. A reboiler is located at the outlet at the bottom of the solvent recovery tower, and its outlet is connected to the inlet of the resin intermediate tank via a transfer pump. The outlet of the resin intermediate tank is connected to the inlet of the fixed-bed reactor. A condenser is located at the outlet at the top of the fixed-bed reactor, and its outlet is connected to the inlet of the phase separator. The upper outlet of the phase separator is connected to the inlet of the alkaline washing vessel in the siloxane extraction unit, and the bottom outlet of the phase separator is connected to the waste alkali tank. The bottom outlet of the fixed-bed reactor is connected to both the inlet of the fixed-bed reactor and the inlet of the cooler, and the outlet of the cooler is connected to the inlet of the solvent-free resin tank.

[0056] Siloxane extraction unit such as Figure 6As shown, the system includes an alkaline washing kettle, a phase separator, and a refining tower. The inlet of the alkaline washing kettle is connected to the outlet at the top of the phase separator in the resin preparation unit. An alkaline solution preparation tank is also connected to the inlet of the alkaline washing kettle, and the inlet of the alkaline washing kettle is also connected to the tail gas condenser. The outlet of the alkaline washing kettle is connected to the inlet at the middle of the phase separator. The outlet at the bottom of the phase separator is connected to the inlet of the alkaline washing kettle and the waste alkaline solution tank via a reflux pump. The outlet at the top of the phase separator is connected to the inlet of the refining tower via a transfer pump. The outlet at the bottom of the refining tower is connected to the reboiler of the refining tower. The outlet of the reboiler of the refining tower is connected to the siloxane storage tank via a transfer pump. The outlet at the top of the refining tower is connected to the condenser. A solvent recovery tank is connected to the outlet of the condenser. The outlet of the solvent recovery tank is connected to the inlet of the refining tower and the solvent storage tank via a reflux pump.

[0057] Example 1: A continuous method for preparing solvent-free silicone resin This embodiment describes a solvent-free continuous method for preparing silicone resin. The siloxane used is a low-boiling-point siloxane. The resin is processed using the aforementioned system and preparation method, as detailed below: 1) Saturated acid solvent hydrolysis loop process Saturated acid solvent hydrolysis loop such as Figure 1 As shown, cyclohexanol is used as the solvent. A mixture of methylchlorosilanes with a boiling range of 80~130℃ (GF01) is used as monomer A, and monomethyltrichlorosilane (M1) is used as monomer B. GF01, M1 and cyclohexanol are added to the mixing tank in a volume ratio of 1:0.2:4 and mixed well. Then, the mixture obtained in the mixing tank and the washing water are added to the static mixer in a volume ratio of GF01 to washing water of 1:6. The mixture is held at 60℃ and 0.01MPa for 10 minutes and then separated by a hydrolysis phase separator to obtain acidic hydrolysate (oil phase), saturated acid solution (aqueous phase) and hydrogen chloride gas (gas phase). The saturated acid solution is returned to the static mixer as part of the washing water. The hydrogen chloride gas is condensed and purified and returned to the direct method methylchlorosilane monomer synthesis system as 99% HCl for recycling. The acidic hydrolysate enters the water washing loop for washing.

[0058] 2) Water washing loop process Water washing loop process such as Figure 2As shown, the acidic hydrolysate undergoes a series of processes including primary water washing, primary phase separation, secondary water washing, secondary phase separation, tertiary water washing, and tertiary phase separation. The resulting neutral material (i.e., the tertiary oil phase, with a chloride ion content of 80 ppm) is then introduced into the siloxane extraction process for coarse separation. The aqueous phases generated after each phase separation are partially returned to the corresponding water washing process, while the remainder enters the next stage of water washing. The primary aqueous phase is partially returned to the primary water washing process, and the remaining primary aqueous phases undergo neutralization, ultrafiltration / nanofiltration, reverse osmosis, and evaporation sequentially. The volume ratio of the acidic hydrolysate to the washing water added to each stage of the water washing reactor is 1:1. The residence time in each stage of the water washing reactor is 15 minutes, and the reaction temperature is 60°C. Ultrasonic crushing is used in the primary, secondary, and tertiary water washing processes at a frequency of 20 kHz, with a cycle of 10 seconds on and 30 seconds off.

[0059] The volume ratio of the tertiary aqueous phase separated by the three-stage phase separator returning to the tertiary washing tank to the amount entering the secondary washing tank is 20:0.75. The volume ratio of the secondary aqueous phase separated by the secondary phase separator returning to the secondary washing tank to the amount entering the primary washing tank is 20:1. The volume ratio of the primary aqueous phase separated by the primary phase separator returning to the primary washing tank to the amount entering the neutralization tank is 20:1.

[0060] The brine obtained after neutralization of the primary aqueous phase has a salt content of 20 g / L and an oil content of 30 g / L. After oil removal by nanofiltration membrane, oil-rich brine and purified brine with a volume ratio of 1:3 are produced. All of the oil-rich brine enters the secondary water washing process. The purified brine is reverse osmosis to produce fresh water and concentrated water with a volume ratio of 5:1. All of the fresh water enters the tertiary water washing process. The concentrated water is evaporated to produce condensate and sodium chloride. All of the condensate is also returned to the tertiary water washing process.

[0061] 3) Siloxane extraction process Siloxane extraction process as follows Figure 3 As shown, neutral material enters the coarse separation column for coarse separation. The top temperature of the coarse separation column is 115℃, the top pressure is 0.01 MPa, the theoretical number of plates is 10, and the reflux ratio is 1.5. A coarse separation column reboiler is installed at the bottom of the coarse separation column, and the temperature of the coarse separation column reboiler is 135℃. The volume ratio of the neutral material entering the coarse separation column to the output of the coarse separation column reboiler (i.e., the silicone resin containing solvent) and the output of the condensate from the top condenser of the coarse separation column (i.e., the low-boiling-point siloxane mixture) is 10:9.9:0.1.

[0062] The low-boiling-point siloxane mixture obtained after coarse separation was alkali-washed in an alkaline washing tank using a 5wt% NaOH solution (alkaline solution). The residence time in the alkaline washing tank was 10 min, the washing temperature was 60℃, and the pressure was 0.9 MPa. The volume ratio of nitrogen flow rate (for hydrogen generation safety protection) to the feed rate to the alkaline washing tank was 15:1. Pressurization during the alkaline washing process suppressed product volatilization and reduced nitrogen flow rate, minimizing entrainment losses.

[0063] After alkaline washing, the aqueous phase is separated by a phase separator. The aqueous phase is returned to the alkaline washing kettle as alkali solution, while the remaining aqueous phase is temporarily stored in a waste alkali solution tank. The oil phase is then purified in a refining tower. The refining tower has a top temperature of 105℃, a top pressure of 0.01 MPa, 20 theoretical plates, and a reflux ratio of 2.0. A reboiler is installed at the bottom of the refining tower, with a temperature of 125℃. The volume ratio of the oil phase entering the refining tower to the reboiler output and the condenser output (i.e., siloxane) at the top of the refining tower is 10:5:5, resulting in a siloxane purity of 99%.

[0064] 4) Resin preparation process Resin preparation process as follows Figure 4 As shown, solvent-containing silicone resin enters a solvent recovery tower for solvent recovery. The top temperature of the solvent recovery tower is 115℃, the top pressure is -0.09 MPa, the theoretical plate number is 15, and the reflux ratio is 0.7. A reboiler is installed at the bottom of the solvent recovery tower, and the temperature of the reboiler is 135℃. The volume ratio of solvent-containing silicone resin to the reboiler output (silicone resin) and the condenser output (recovered solvent) at the top of the solvent recovery tower is 10:1.2:8.8.

[0065] Silicone resin is transported to a stationary reactor, where a 50wt% KOH aqueous solution is added as a catalyst at a concentration of 150 ppm (based on KOH weight). The reaction is carried out at 45°C and -0.098 MPa for 2 hours. Based on customer requirements, when the online viscometer shows the viscosity reaches 90% of the required level, 130 ppm phosphoric acid (based on KOH weight) is added for neutralization for 15 minutes. The hourly nitrogen flow rate (standard) is four times that of the solvent in the reactor (for hydrogen generation safety protection). The resulting silicone resin product has a total residual impurity content of less than 200 ppm and consists of KCl, KH₂PO₄, and K₂HPO₄. The presence of a buffer system in the silicone resin product helps extend its shelf life.

[0066] Example 2: A continuous method for preparing solvent-free silicone resin This embodiment describes a solvent-free continuous method for preparing silicone resin. The siloxane used is a high-boiling-point siloxane. The resin is processed using the aforementioned system and preparation method, as detailed below: 1) Saturated acid solvent hydrolysis loop process Xylene is used as a solvent. A mixture of methylchlorosilanes with a boiling range exceeding 160℃ (GF02) is used as monomer A, and dimethyldichlorosilane (M2) is used as monomer B. GF02, M2 and xylene are added to a mixing tank at a volume ratio of 1:0.3:4 and mixed thoroughly. Then, the mixture obtained in the mixing tank and the washing water are added to a static mixer at a volume ratio of GF02 to washing water of 1:10. The mixture is held at 50℃ and 0.02MPa for 5 minutes and then separated by a hydrolysis phase separator to obtain acidic hydrolysate (oil phase), saturated acid solution (aqueous phase) and hydrogen chloride gas (gas phase). The saturated acid solution is returned to the static mixer as part of the washing water. The hydrogen chloride gas is condensed and purified, and returned to the direct method methylchlorosilane monomer synthesis system as 99% HCl for recycling. The acidic hydrolysate enters the water washing loop for washing.

[0067] 2) Water washing loop process The acidic hydrolysate undergoes a series of washing processes: primary washing, primary phase separation, secondary washing, secondary phase separation, tertiary washing, tertiary phase separation, and quaternary washing and phase separation. The resulting neutral material (i.e., the quaternary oil phase, with a chloride ion content of 250 ppm) is then introduced into the siloxane extraction process for coarse separation. The aqueous phases from each phase separation are partially returned to the corresponding washing process, while the remainder is sent to the next washing process. The primary aqueous phase is partially returned to the primary washing process, and the remaining primary aqueous phases undergo neutralization, ultrafiltration / nanofiltration, reverse osmosis, and evaporation sequentially. The volume ratio of the acidic hydrolysate to the washing water added to each washing vessel is 1:2. The residence time in each washing vessel is 15 minutes, and the reaction temperature is 50°C. Ultrasonic crushing is used in the primary, secondary, and tertiary washing processes at a frequency of 40 kHz, with a 20-second on / 10-second off cycle.

[0068] The volume ratio of the fourth-stage aqueous phase separated by the four-stage phase separator returning to the fourth-stage washing tank to the volume entering the third-stage washing tank is 20:2. The volume ratio of the third-stage aqueous phase separated by the three-stage phase separator returning to the third-stage washing tank to the volume entering the second-stage washing tank is 20:2. The volume ratio of the second-stage aqueous phase separated by the two-stage phase separator returning to the second-stage washing tank to the volume entering the first-stage washing tank is 20:3. The volume ratio of the first-stage aqueous phase separated by the first-stage phase separator returning to the first-stage washing tank to the volume entering the neutralization tank is 20:3.

[0069] The brine obtained after neutralization of the primary aqueous phase has a salt content of 40 g / L and an oil content of 50 g / L. After oil removal by nanofiltration membrane, oil-rich brine and purified brine with a volume ratio of 1:2 are produced. All of the oil-rich brine enters the secondary water washing process. The purified brine is reverse osmosis to produce fresh water and concentrated water with a volume ratio of 3:1. All of the fresh water enters the tertiary water washing process. The concentrated water is evaporated to produce condensate and sodium chloride. All of the condensate is also returned to the tertiary water washing process.

[0070] 3) Resin preparation process Neutral material enters the solvent recovery tower for solvent recovery. The top temperature of the solvent recovery tower is 85℃, the top pressure is -0.09 MPa, the theoretical plate number is 10, and the reflux ratio is 0.7. A reboiler is installed at the bottom of the solvent recovery tower, and the temperature of the reboiler is 110℃. The volume ratio of neutral material to the output of the reboiler (silicone resin) and the output of the condenser at the top of the solvent recovery tower (recovered solvent) is 10:1.4:8.6.

[0071] Silicone resin is fed into a stationary reactor, and a sulfonic acid-based cationic polystyrene resin catalyst is added at a rate of 300 ppm (based on the weight of H2SO4 converted from the loaded acid). The reaction is carried out at 60°C and -0.095 MPa for 2 hours. Based on customer requirements, when the online viscometer shows a viscosity reaching 98% of the required level, the product is cooled to obtain a guaranteed silicone resin product. The high-value siloxane mixture formed during the polycondensation reaction is condensed in a condenser, then dehydrated by a phase separator, and the recovered oil phase is sent to an alkaline washing kettle for further processing.

[0072] 4) Siloxane extraction process The high-value siloxane mixture removed during the polycondensation reaction is condensed in a condenser and dehydrated in a phase separator. The recovered oil phase is then transported to an alkaline washing reactor, where it is washed using a 5wt% NaOH solution (alkaline solution). The residence time in the alkaline washing reactor is 10 min, the washing temperature is 80℃, and the pressure is 0.9 MPa. The volume ratio of nitrogen flow rate (for hydrogen generation safety protection) to the feed rate is 15:1. Pressurization during the alkaline washing process suppresses product volatilization and reduces nitrogen flow rate, minimizing entrainment losses.

[0073] After alkaline washing, the aqueous phase is separated by a phase separator. The aqueous phase is returned to the alkaline washing kettle as alkali solution, while the remaining aqueous phase is temporarily stored in a waste alkali solution tank. The oil phase is then purified in a refining tower. The refining tower has a top temperature of 105℃, a top pressure of 0.01 MPa, 20 theoretical plates, and a reflux ratio of 2.0. A reboiler is installed at the bottom of the refining tower, with a temperature of 125℃. The volume ratio of the oil phase entering the refining tower to the reboiler output (i.e., siloxane) and the condenser output (i.e., solvent) at the top of the refining tower is 10:5:5, resulting in a siloxane purity of 99%.

[0074] Example 3: A continuous method for preparing solvent-free silicone resin This embodiment describes a solvent-free continuous method for preparing silicone resin. The siloxane used is a low-boiling-point siloxane. The resin is processed using the aforementioned system and preparation method, as detailed below: 1) Saturated acid solvent hydrolysis loop process Anisole was used as the solvent, silicon tetrachloride (SiCl4) as monomer A, and trimethylchlorosilane (M3) as monomer B. The monomers were added to a static mixer in two stages. The first addition consisted of SiCl4, M3, and anisole added to the mixing vessel at a volume ratio of 1:0.2:4 and mixed thoroughly. Then, the mixture from the mixing vessel, along with the wash water, was added to the static mixer at a volume ratio of SiCl4 to wash water of 1:6. The mixture was held at 10°C and 0.05 MPa for 2 minutes. The second addition was then performed, with M3 and anisole added to the mixing vessel at a volume ratio of 0.1:1. The mixture is then homogenized, and then the second mixture and the second wash water obtained in the mixing vessel are added to the static mixer at a volume ratio of M3 to the second wash water of 0.1:6. The mixture is held at 10℃ and 0.05MPa for 15 minutes, and then separated by a hydrolysis phase separator to obtain acidic hydrolysate (oil phase), saturated acid solution (aqueous phase), and hydrogen chloride gas (gas phase). The saturated acid solution is returned to the static mixer as part of the wash water, and the hydrogen chloride gas is condensed and purified and returned to the direct method methylchlorosilane monomer synthesis system as 99% HCl for recycling. The acidic hydrolysate enters the water washing loop process for water washing.

[0075] 2) Water washing loop process The acidic hydrolysate undergoes a series of washing processes: primary washing, primary phase separation, secondary washing, secondary phase separation, tertiary washing, tertiary phase separation, quaternary washing, quaternary phase separation, quinary washing, and quinary phase separation. The resulting neutral material (i.e., the fifth-stage oil phase, with a chloride ion content of 30 ppm) is then introduced into the siloxane extraction process for coarse separation. The aqueous phases from each stage of phase separation are partially returned to the corresponding stage of washing, while the remainder is sent to the next stage of washing. The primary aqueous phase is partially returned to the primary washing process, and the remaining primary aqueous phase undergoes neutralization, ultrafiltration / nanofiltration, reverse osmosis, and evaporation. The volume ratio of the acidic hydrolysate to the washing water added to each stage of washing is 1:3. The residence time in each stage of washing is 10 minutes, and the reaction temperature is 40°C. The primary and secondary washing processes are equipped with ultrasonic crushing at a frequency of 30 kHz, operating in a 30-second on-time, 10-second off-time cycle.

[0076] The volume ratio of the fifth-stage aqueous phase separated by the five-stage phase separator returning to the fifth-stage washing tank to the volume entering the fourth-stage washing tank is 20:3.2. The volume ratio of the fourth-stage aqueous phase separated by the four-stage phase separator returning to the fourth-stage washing tank to the volume entering the third-stage washing tank is 20:3.2. The volume ratio of the third-stage aqueous phase separated by the three-stage phase separator returning to the third-stage washing tank to the volume entering the second-stage washing tank is 20:3.2. The volume ratio of the second-stage aqueous phase separated by the two-stage phase separator returning to the second-stage washing tank to the volume entering the first-stage washing tank is 20:4. The volume ratio of the first-stage aqueous phase separated by the first-stage phase separator returning to the first-stage washing tank to the volume entering the neutralization tank is 20:4.

[0077] The brine obtained after neutralization of the primary aqueous phase has a salt content of 30 g / L and an oil content of 20 g / L. After oil removal by nanofiltration membrane, oil-rich brine and purified brine with a volume ratio of 1:4 are produced. All of the oil-rich brine enters the secondary water washing process. The purified brine is reverse osmosis to produce fresh water and concentrated water with a volume ratio of 4:1. All of the fresh water enters the tertiary water washing process. The concentrated water is evaporated to produce condensate and sodium chloride. All of the condensate is also returned to the tertiary water washing process.

[0078] 3) Siloxane extraction process Neutral material enters the coarsening column for coarsening. The top temperature of the coarsening column is 105℃, the top pressure is 0.01 MPa, the theoretical number of plates is 10, and the reflux ratio is 1.2. A reboiler is installed at the bottom of the coarsening column, with a temperature of 125℃. The volume ratio of the neutral material entering the coarsening column to the output from the reboiler (i.e., solvent-containing silicone resin) and the condensate output from the condenser at the top of the coarsening column (i.e., a low-boiling-point siloxane mixture) is 10:9.95:0.05.

[0079] The low-boiling-point siloxane mixture obtained after coarse separation was alkali-washed in an alkaline washing tank using a 5wt% NaOH solution (alkaline solution). The residence time in the alkaline washing tank was 5 min, the washing temperature was 40℃, and the pressure was 0.9 MPa. The volume ratio of nitrogen flow rate (for hydrogen generation safety protection) to the feed rate to the alkaline washing tank was 15:1. Pressurization during the alkaline washing process suppressed product volatilization and reduced nitrogen flow rate, minimizing entrainment losses.

[0080] After alkaline washing, the aqueous phase is separated by a phase separator. The aqueous phase is returned to the alkaline washing kettle as alkali solution, while the remaining aqueous phase is temporarily stored in a waste alkali solution tank. The oil phase is then purified in a refining tower. The refining tower has a top temperature of 105℃, a top pressure of 0.01 MPa, 15 theoretical plates, and a reflux ratio of 1.5. A reboiler is installed at the bottom of the refining tower, with a temperature of 125℃. The volume ratio of the oil phase entering the refining tower to the reboiler output and the condenser output (i.e., siloxane) at the top of the refining tower is 10:2:8, resulting in a siloxane purity of 99%.

[0081] 4) Resin preparation process Solvent-containing silicone resin enters a solvent recovery tower for solvent recovery. The tower has a top temperature of 95°C, a top pressure of -0.09 MPa, 15 theoretical plates, and a reflux ratio of 0.5. A reboiler is installed at the bottom of the tower, with a temperature of 115°C. The volume ratio of the solvent-containing silicone resin to the reboiler output (resin) and the condenser output (recovered solvent) is 10:0.9:9.1.

[0082] The resin is transported to a stationary reactor, where a 50wt% NaOH aqueous solution is added as a catalyst at a concentration of 80ppm (based on NaOH weight). The reaction is carried out at 45℃ and -0.098MPa for 1 hour. Based on customer requirements, when the online viscometer shows the viscosity reaches 90% of the required level, 50ppm phosphoric acid (based on NaOH weight) is added for neutralization for 15 minutes. The hourly nitrogen flow rate (standard) is four times that of the solvent in the reactor (for hydrogen generation safety protection). The resulting silicone resin product has a total residual impurity content of less than 100ppm and consists of KCl, NaH2PO4, and Na2HPO4. The presence of a buffer system in the silicone resin product helps extend its shelf life.

[0083] Example 4: A continuous method for preparing solvent-free silicone resin This embodiment describes a solvent-free continuous method for preparing silicone resin. The siloxane used is a high-boiling-point siloxane. The resin is processed using the aforementioned system and preparation method, as detailed below: 1) Saturated acid solvent hydrolysis loop process A mixture of dichloroethyl ether and 120# solvent oil (volume ratio 28:72, referred to as mixed solvent 1) was used as the solvent. Dimethyldichlorosilane (M2) was used as monomer A, phenyltrichlorosilane (Ph1) as monomer B, and diphenyldichlorosilane (Ph2) as monomer C. M2, Ph1, Ph2, and mixed solvent 1 were added to a mixing vessel at a volume ratio of 1:1.5:3:6 and mixed thoroughly. Then, the mixture was further prepared at a volume ratio of M2 to washing water of 1:12. The mixture obtained in the reactor and the wash water are added to a static mixer and held at 60°C and 0.08 MPa for 30 minutes. Then, it is separated by a hydrolysis phase separator to obtain acidic hydrolysate (oil phase), saturated acid solution (aqueous phase), and hydrogen chloride gas (gas phase). The saturated acid solution is returned to the static mixer as part of the wash water. The hydrogen chloride gas is condensed and purified and returned to the direct method methylchlorosilane monomer synthesis system as 99% HCl for recycling. The acidic hydrolysate enters the water washing loop process for washing.

[0084] 2) Water washing loop process The acidic hydrolysate undergoes sequential primary washing, primary phase separation, secondary washing, secondary phase separation, tertiary washing, tertiary phase separation, and quaternary washing and phase separation. The resulting neutral material (i.e., the quaternary oil phase, with a chloride ion content of 100 ppm) enters the siloxane extraction process for coarse separation. The aqueous phases from each phase separation are partially returned to the corresponding washing stage, while the remainder enters the next washing stage. The primary aqueous phase is partially returned to the primary washing stage, and the remaining primary aqueous phase undergoes neutralization, ultrafiltration / nanofiltration, reverse osmosis, and evaporation sequentially. The volume ratio of acidic hydrolysate to the washing water added to each washing stage is 1:1.5. The residence time in each washing stage is 20 minutes, and the reaction temperature is 60℃. Ultrasonic crushing is used in the primary, secondary, and tertiary washing stages at a frequency of 40 kHz, operating in a 20-second on-time, 10-second off-time cycle.

[0085] The volume ratio of the fourth-stage aqueous phase separated by the four-stage phase separator returning to the fourth-stage washing tank to the volume entering the third-stage washing tank is 20:2. The volume ratio of the third-stage aqueous phase separated by the three-stage phase separator returning to the third-stage washing tank to the volume entering the second-stage washing tank is 20:2. The volume ratio of the second-stage aqueous phase separated by the two-stage phase separator returning to the second-stage washing tank to the volume entering the first-stage washing tank is 20:3. The volume ratio of the first-stage aqueous phase separated by the first-stage phase separator returning to the first-stage washing tank to the volume entering the neutralization tank is 20:3.

[0086] The brine obtained after neutralization of the primary aqueous phase has a salt content of 30 g / L and an oil content of 40 g / L. After oil removal by nanofiltration membrane, oil-rich brine and purified brine with a volume ratio of 1:2 are produced. All of the oil-rich brine enters the secondary water washing process. The purified brine is reverse osmosis to produce fresh water and concentrated water with a volume ratio of 3:1. All of the fresh water enters the tertiary water washing process. The concentrated water is evaporated to produce condensate and sodium chloride. All of the condensate is also returned to the tertiary water washing process.

[0087] 3) Resin preparation process Neutral material enters the solvent recovery tower for solvent recovery. The top temperature of the solvent recovery tower is 80℃, the top pressure is -0.08 MPa, the theoretical plate number is 12, and the reflux ratio is 1. A reboiler is installed at the bottom of the solvent recovery tower, and the temperature of the reboiler is 105℃. The volume ratio of neutral material to the output of the reboiler (silicone resin) and the output of the condenser at the top of the solvent recovery tower (recovered solvent) is 10:3.7:6.3.

[0088] Silicone resin is fed into a stationary reactor, and a silanized alumina cationic resin catalyst is added at a rate of 250 ppm (based on the weight of H2SO4 converted from the loaded acid). The reaction is carried out at 70°C and -0.095 MPa for 3 hours. Based on customer requirements, when the online viscometer shows a viscosity reaching 98% of the required level, the product is cooled to obtain a guaranteed silicone resin product. The high-value siloxane mixture formed during the polycondensation reaction is condensed in a condenser, then dehydrated by a phase separator, and the recovered oil phase is sent to an alkaline washing kettle for further processing.

[0089] 4) Siloxane extraction process The high-value siloxane mixture removed during the polycondensation reaction is condensed in a condenser and dehydrated in a phase separator. The recovered oil phase is then transported to an alkaline washing reactor, where it is washed using a 5wt% NaOH solution (alkaline solution). The residence time in the alkaline washing reactor is 10 min, the washing temperature is 60℃, and the pressure is 0.9 MPa. The volume ratio of nitrogen flow rate (for hydrogen generation safety protection) to the feed rate is 15:1. Pressurization during the alkaline washing process suppresses product volatilization and reduces nitrogen flow rate, minimizing entrainment losses.

[0090] After alkaline washing, the aqueous phase is separated by a phase separator. The aqueous phase is returned to the alkaline washing kettle as alkali solution, while the remaining aqueous phase is temporarily stored in a waste alkali solution tank. The oil phase is then purified in a refining tower. The refining tower has a top temperature of 105℃, a top pressure of 0.01 MPa, 20 theoretical plates, and a reflux ratio of 2.0. A reboiler is installed at the bottom of the refining tower, with a temperature of 125℃. The volume ratio of the oil phase entering the refining tower to the reboiler output (i.e., siloxane) and the condenser output (i.e., solvent) at the top of the refining tower is 10:5:5, resulting in a siloxane purity of 99%.

[0091] Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A process for the solvent-free continuous production of silicone resins, characterized in that, The preparation method recovers siloxane as low-boiling siloxane, comprising the following steps: 1) saturated acid solvent hydrolysis loop process After the solvent, monomer A and monomer B are uniformly mixed, hydrolysis reaction is carried out with the saturated acid liquid in the loop, and then separation is carried out to obtain acidic hydrolysate for entering the water washing loop, the separated saturated acid liquid is returned to the hydrolysis reaction after supplementing water consumed by reaction, and the separated hydrogen chloride gas is returned to the direct method methyl chlorosilane monomer synthesis system for recycling as 99% HCl. 2) water washing loop process The acidic hydrolysate is subjected to multi-stage water washing and multi-stage phase separation to obtain corresponding water phases and oil phases, part of each water phase is returned to the water washing process as washing water, the remaining water phase is used as washing water in the upper-stage water washing process, and each oil phase enters the next-stage water phase process for further water washing; wherein part of the first-stage water phase obtained by first-stage phase separation is returned to the first-stage water washing process as washing water, and the remaining first-stage water phase is sequentially subjected to neutralization into brine, filtration, dialysis and evaporation to obtain sodium chloride. The filtered oil-rich brine enters the second-stage water washing process, and the dialyzed brine and the evaporated condensed water enter the third-stage water washing process. The oil phase obtained by the last-stage phase separation is neutral material and is fed into a crude fraction column for separation. 3) siloxane extraction process The neutral material is fed into the crude fraction column for preliminary separation, low-boiling high-value siloxane mixture is recovered at the top, and resin and solvent not containing low-boiling high-value siloxane are recovered at the bottom and are subjected to treatment by a crude fraction column reboiler to obtain silicic resin containing solvent, which is then fed into a solvent recovery column. The low-boiling high-value siloxane mixture is condensed and then fed into an alkali washing kettle for alkali washing by using alkali liquor. The liquid after alkali washing is separated, the water phase is returned to the alkali washing kettle as alkali liquor, and the separated oil phase is fed into a refining column for refining, the product is recovered at the top, and solvent is recovered at the bottom. The product recovered at the top is condensed and used as siloxane product. 4) resin preparation process The silicic resin is fed into the solvent recovery column for solvent recovery, and the recovered solvent and low-boiling siloxane are obtained at the top. The silicic resin at the bottom of the solvent recovery column is subjected to treatment by a recovery column reboiler, fed into a fixed reactor for polycondensation reaction, and then packed as silicic resin product.

2. The solvent-free silicone resin continuous process according to claim 1, characterized in that, In step 1), the solvent is a single solvent or a mixed solvent of two or more solvents, and the δ d > 15, the δ h > 0.5~5, the δ p > 0.5~7, the solvent is insoluble in water and can exist stably for a long time in an environment with PH < 3 and PH > 10; the boiling point of the solvent is 110~200℃; Monomer A and monomer B are different chlorosilanes; or, monomer A and monomer B are chlorosilanes and siloxanes; or, monomer A and monomer B are organic silicic high-boiling substance, organic silicic low-boiling substance and organic silicic slurry supernatant. The average functionality of monomer A and monomer B after mixing is controlled to be 1.5-2.

3. The solvent-free silicone resin continuous process according to claim 1 or 2, characterized in that, In step 1), when a single solvent is used, the solvent is toluene, xylene, anisole or cyclohexanol; when a mixed solvent is used, the solvent is a mixture of n-butanol and 180# solvent oil, a mixture of cyclohexanol and S150 industrial solvent oil, a mixture of dichloroether and 180# solvent oil, or a mixture of chlorohexane and S150 industrial solvent oil; in step 3), the alkali liquor is NaOH solution or NaHCO3 solution; in step 4), during the polycondensation reaction, a strong alkaline catalyst or a cationic strong acid resin catalyst is used for resin polycondensation.

4. The solvent-free silicone resin continuous process according to claim 1 or 2, characterized in that, In step 1), the temperature of the hydrolysis reaction is 0-80℃, the time is 1-60 min, and the pressure is 0.01-0.1 Mpa; In step 2), the temperature of each stage of water washing is 0-80℃, and the time is 5-60 min.

5. A system for solventless silicone resin continuous process preparation, characterized by, The preparation method of any one of claims 1-4 is prepared by the solvent-free silicone resin continuous preparation system, which comprises a saturated acid solvent hydrolysis loop unit, a water washing loop unit, a siloxane extraction unit, and a resin preparation unit; The saturated acid solvent hydrolysis loop unit comprises a mixing kettle, a static mixer, a hydrolysis phase separator, and a hydrolyzate intermediate tank; the outlet of the mixing kettle is connected with the static mixer, a soft water inlet pipe is arranged at the inlet of the static mixer, the outlet of the static mixer is connected with the inlet of the middle part of the hydrolysis phase separator, the outlet at the bottom of the hydrolysis phase separator is connected with the inlet of the static mixer, a condensation purification device is arranged at the outlet at the top of the hydrolysis phase separator, the condensation purification device is provided with two outlets, one outlet is used for recycling HCl, and the other outlet is connected with the inlet of the hydrolyzate intermediate tank; the hydrolyzate intermediate tank is provided with two outlets, which are respectively connected with the first-stage water washing kettle of the water washing loop unit and the inlet of the middle part of the hydrolysis phase separator; The water washing loop unit comprises multiple-stage water washing kettles, multiple-stage phase separators, a neutralization tank, an ultrafiltration / nanofiltration device, a reverse osmosis device, and an evaporator; the outlet of each stage of water washing kettle is connected with the inlet of the phase separator of the stage, the outlet at the upper part of each stage of phase separator is connected with the inlet of the next stage of water washing kettle, and the outlet at the bottom of each stage of phase separator is respectively connected with the inlet of the water washing kettle of the stage and the inlet of the water washing kettle of the previous stage; The inlet of the first-stage water washing kettle is connected with the outlet of the hydrolyzate intermediate tank of the saturated acid solvent hydrolysis loop unit; the outlet at the bottom of the first-stage phase separator is respectively connected with the inlet of the first-stage water washing kettle and the inlet of the neutralization tank, the outlet of the neutralization tank is connected with the inlet of the ultrafiltration / nanofiltration device, the ultrafiltration / nanofiltration device is provided with two outlets, one outlet is connected with the inlet of the second-stage water washing kettle and is used for conveying the oil-rich brine generated by the ultrafiltration / nanofiltration to the second-stage water washing kettle, and the other outlet is connected with the reverse osmosis device, the permeation treatment of the reverse osmosis membrane generates fresh water and concentrated water, the fresh water outlet of the reverse osmosis device is connected with the inlet of the third-stage water washing kettle, the concentrated water outlet is connected with the inlet of the evaporator, and the condensed water outlet of the evaporator is connected with the inlet of the third-stage water washing kettle; The outlet at the upper part of the last-stage phase separator is connected with the inlet of the coarse separation tower of the siloxane extraction unit; The siloxane extraction unit comprises a coarse separation tower, an alkali washing kettle, a phase separator, and a refining tower; the inlet of the coarse separation tower is connected with the outlet of the last-stage water washing intermediate tank of the water washing loop unit, the outlet at the bottom of the coarse separation tower is connected with the inlet of the solvent recovery tower of the resin preparation unit, the outlet at the top of the coarse separation tower is respectively connected with the inlet of the coarse separation tower and the inlet of the alkali washing kettle; the outlet of the alkali washing kettle is connected with the inlet of the phase separator; the outlet at the bottom of the phase separator is connected with the inlet of the alkali washing kettle and a waste alkali tank, the outlet at the upper part of the phase separator is connected with the inlet of the refining tower, the outlet at the bottom of the refining tower is connected with a solvent storage tank, and the outlet at the top of the refining tower is respectively connected with the inlet of the refining tower and a siloxane storage tank. The resin preparation unit comprises a solvent recovery tower, a resin intermediate tank, a fixed bed reactor, a cooler, a phase separator, a cooler and a solvent-free resin tank; the inlet of the solvent recovery tower is communicated with the outlet of the reboiler of the coarse separation tower in the siloxane extraction unit; the outlets at the top of the solvent recovery tower are respectively communicated with the inlet of the solvent recovery tower and the solvent storage tank; the outlet at the bottom of the solvent recovery tower is communicated with the inlet of the fixed bed reactor, the outlet at the top of the fixed bed reactor is communicated with the inlet of the phase separator, the outlet at the upper part of the phase separator is communicated with the inlet of the solvent storage tank, and the outlet at the bottom of the phase separator is communicated with the waste lye tank; The outlet at the bottom of the fixed bed reactor is respectively communicated with the inlet of the fixed bed reactor and the inlet of the cooler, and the outlet of the cooler is communicated with the inlet of the solvent-free resin tank.

6. A process for the solvent-free continuous production of silicone resins, characterized in that, The preparation method recovers high-boiling siloxane, comprising the following steps: 1) saturated acid solvent hydrolysis loop process After the solvent, monomer A and monomer B are uniformly mixed, hydrolysis reaction is carried out with the saturated acid liquid in the loop, and then separation is carried out to obtain acidic hydrolysate, which is used to enter the water washing loop, and the separated saturated acid liquid is returned to the hydrolysis reaction after supplementing water consumed in the reaction, and the separated hydrogen chloride gas is returned to the direct method methyl chlorosilane monomer synthesis system for recycling as 99% HCl. 2) water washing loop process The acidic hydrolysate is subjected to multi-stage water washing and multi-stage phase separation to obtain corresponding water phases and oil phases, part of each water phase is returned to the water washing process as washing water, the remaining water phase is used as washing water in the next-stage water washing process, and each oil phase enters the next-stage water phase process for further water washing; wherein part of the first-stage water phase obtained through first-stage phase separation is returned to the first-stage water washing process as washing water, and the remaining first-stage water phase is sequentially subjected to neutralization into brine, filtration, dialysis and evaporation to obtain sodium chloride; The filtered oil-rich brine enters the second-stage water washing process, and the dialyzed brine and the evaporated condensate enter the third-stage water washing process; The oil phase obtained through the last-stage phase separation is used as neutral material and enters the solvent recovery tower for solvent recovery; 3) resin preparation process The neutral material enters the solvent recovery tower for solvent recovery, and the recovered solvent and low-boiling siloxane are obtained at the top of the tower; The silicon resin at the bottom of the solvent recovery tower is treated by the reboiler of the recovery tower and then delivered to the fixed reactor for polycondensation reaction to obtain a silicon resin product; The high-value siloxane mixture removed through the polycondensation reaction is condensed and phase-separated, and the oil phase is delivered to an alkali washing kettle for alkali washing; 4) siloxane extraction process The high-value siloxane mixture is condensed and then delivered to the alkali washing kettle for alkali washing by using lye; The liquid after alkali washing is separated, the water phase part is returned to the alkali washing kettle as lye, and the separated oil phase is delivered to a refining tower for refining, and the recovered siloxane product is obtained at the bottom of the tower and the solvent is obtained at the top of the tower.

7. The solventless silicone resin continuous process of claim 6, wherein, In step 1), the solvent is a single solvent or a mixture of two or more solvents, and the solvent's δ d >15, δ h 0.5~5, δ p The pH ranges from 0.5 to 7; the solvent is insoluble in water and can remain stable in environments with pH < 3 and pH > 10 for a long time; the solvent boiling point is 110 to 200℃. Monomer A and monomer B are different chlorosilanes; Alternatively, monomer A and monomer B are chlorosilanes and siloxanes; Alternatively, monomer A and monomer B are organic silicon high-boiling substances, organic silicon low-boiling substances and organic silicon slurry supernatant; The average functionality of monomer A and monomer B after mixing is controlled to be 1.5-2.

8. The solvent-free silicone resin continuous process according to claim 6 or 7, characterized in that, In step 1), when a single solvent is used, the solvent is toluene, xylene, anisole or cyclohexanol. When the mixed solvent is used, the solvent is a mixture of n-butanol and 180# solvent oil, a mixture of cyclohexanol and S150 industrial solvent oil, a mixture of dichloroether and 180# solvent oil, or a mixture of chlorohexane and S150 industrial solvent oil; In step 3), during the polycondensation reaction, a strong alkaline catalyst or a cationic strong acid resin catalyst is used for resin polycondensation; In step 4), the lye is NaOH solution or NaHCO3 solution.

9. The solvent-free silicone resin continuous process according to claim 6 or 7, characterized in that, In step 1), the temperature of the hydrolysis reaction is 0-80℃, the time is 1-60min, and the pressure is 0.01-0.1Mpa; In step 2), the temperature of each stage of water washing is 0-80℃, and the time is 5-60min.

10. A system for solventless silicone resin continuous process preparation, characterized by, The preparation method of any one of claims 6-9 uses the solvent-free silicone resin continuous preparation system to prepare the solvent-free silicone resin, and the preparation system comprises a saturated acid solvent hydrolysis loop unit, a water washing loop unit, a siloxane extraction unit, and a resin preparation unit; The saturated acid solvent hydrolysis loop unit comprises a mixing kettle, a static mixer, a hydrolysis phase separator, and a hydrolyzate intermediate tank. The outlet of the mixing kettle is communicated with the static mixer. A soft water inlet pipe is arranged at the inlet of the static mixer. The outlet of the static mixer is communicated with the inlet of the middle part of the hydrolysis phase separator. The outlet at the bottom of the hydrolysis phase separator is communicated with the inlet of the static mixer. A condensation purification device is arranged at the outlet at the top of the hydrolysis phase separator. The condensation purification device is provided with two outlets. One outlet is used for recycling HCl, and the other outlet is communicated with the inlet of the hydrolyzate intermediate tank. The hydrolyzate intermediate tank is provided with two outlets, which are respectively communicated with the first-stage water washing kettle of the water washing loop unit and the inlet of the middle part of the hydrolysis phase separator. The water washing loop unit comprises multiple-stage water washing kettles, multiple-stage phase separators, a neutralization tank, an ultrafiltration / nanofiltration device, a reverse osmosis device, and an evaporator. The outlets of the multiple-stage water washing kettles are respectively communicated with the inlets of the multiple-stage phase separators. The outlets at the upper parts of the multiple-stage phase separators are respectively communicated with the inlets of the next-stage water washing kettles. The outlets at the bottoms of the multiple-stage phase separators are respectively communicated with the inlets of the water washing kettles and the inlets of the previous-stage water washing kettles. The inlet of the first-stage water washing kettle is communicated with the outlet of the hydrolyzate intermediate tank of the saturated acid solvent hydrolysis loop unit. The outlet at the bottom of the first-stage phase separator is respectively communicated with the inlet of the first-stage water washing kettle and the inlet of the neutralization tank. The outlet of the neutralization tank is communicated with the inlet of the ultrafiltration / nanofiltration device. The ultrafiltration / nanofiltration device is provided with two outlets. One outlet is communicated with the inlet of the second-stage water washing kettle, and is used for conveying the oil-rich brine generated by the ultrafiltration / nanofiltration to the second-stage water washing kettle. The other outlet is communicated with the reverse osmosis device. Fresh water and concentrated water are generated by the reverse osmosis membrane permeation treatment. The fresh water outlet of the reverse osmosis device is communicated with the inlet of the third-stage water washing kettle. The concentrated water outlet is communicated with the inlet of the evaporator. The condensed water outlet of the evaporator is communicated with the inlet of the third-stage water washing kettle. The outlet at the upper part of the last-stage phase separator is communicated with the inlet of the solvent recovery column of the resin preparation unit. The resin preparation unit comprises a solvent recovery tower, a resin intermediate tank, a fixed bed reactor, a cooler, a phase separator, a cooler and a solvent-free resin tank; the inlet of the solvent recovery tower is communicated with the outlet at the upper part of the last stage phase separator; the outlet at the top of the solvent recovery tower is respectively communicated with the inlet of the solvent recovery tower and the solvent storage tank; the outlet at the bottom of the solvent recovery tower is communicated with the inlet of the fixed bed reactor, the outlet at the top of the fixed bed reactor is communicated with the inlet of the phase separator, the outlet at the upper part of the phase separator is communicated with the inlet of the caustic washing kettle in the siloxane extraction unit, and the outlet at the bottom of the phase separator is communicated with the waste lye tank; The outlet at the bottom of the fixed bed reactor is respectively communicated with the inlet of the fixed bed reactor and the inlet of the cooler, and the outlet of the cooler is communicated with the inlet of the solvent-free resin tank; The siloxane extraction unit comprises a caustic washing kettle, a phase separator and a refining tower; the inlet of the caustic washing kettle is communicated with the outlet at the upper part of the phase separator in the resin preparation unit, and the outlet of the caustic washing kettle is communicated with the inlet of the phase separator; the outlet at the bottom of the phase separator is communicated with the inlet of the caustic washing kettle and the waste lye tank, the outlet at the upper part of the phase separator is communicated with the inlet of the refining tower, the outlet at the bottom of the refining tower is communicated with a refining tower reboiler, the outlet of the refining tower reboiler is communicated with a siloxane storage tank, the outlet at the top of the refining tower is communicated with a condenser, the outlet of the condenser is communicated with a solvent recovery tank, and the outlet of the solvent recovery tank is respectively communicated with the inlet of the refining tower and the solvent storage tank.

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